Various fields of production control, schedule control, and sequence control or from management to services including these control elements, are remarkably computerized with the progress of computers and microprocessors. In computerizing them, programs or devices are individually created, or software or devices limited in their application field, application hierarchy, and industrial field are being utilized.
For example, business work executed by the division of labor is characterized by distributed processing in individual unit organizations having a holonic architecture, and furthermore, the following functions are required in business work executed by the division of labor:
(1) provide the necessary functions for the execution of a set of missions and self-preservation selected from such functions as management, resource management, marketing and product development, sales, engineering, procurement and storage, production, logistics, construction, and services; and
(2) deliver ordered items, information (documents) or work/services within the designated delivery time in response to external orders.
On the above-mentioned premises, the type of operations actually executed by individual unit organizations of the business work are:
1. to receive inquiries and prepare and submit quotations;
2. to make production plans for ordered items, produce the items and carry out schedule control, cost control, and quality control;
3. to make plans for purchasing and sub-contracting and place an order to the sub-contractor through the process of inquiry/quotation and control purchasing and sub-contracting; and
4. upon completion of the above, to deliver/bill them, receive payment, and further process any complaints and provide services.
In the above form of operations, it is important to follow the sequence of operations and scheduled dates, and the following methods are conventionally employed for this purpose.
The first method is the explosion of orders into component requirements, wherein the components necessary to produce an ordered item are listed using the bills of material. It is checked whether or not the required amount is available at the scheduled date, and if there is a shortage, an additional order is made by a sub-order and it is also checked whether or not the ordered item can be completed on the scheduled date.
The second method is the explosion of orders into operation/resource requirements, wherein the sequence for producing an ordered item is selected from the process chart. It is checked whether or not the necessary resources such as manpower, equipments, etc. are available at the scheduled date, and if not, a countermeasure such as sub-contracting or overtime work is taken.
The third method is the PERT technique, wherein the operations for producing an ordered item are listed and are sequentially connected to each other with arrows to make a network, and whether a plan for producing the item is possible or not is checked from the required period of time and resources necessary for the individual operations.
The fourth method is the Gantt chart, wherein the components necessary to produce an ordered item are listed and the operational stages for producing the individual components are established and whether a plan for producing the item is possible or not is checked from the individual required periods of time and resources necessary for the individual operational stages.
The fifth method is sequence control, wherein all previously presumable conditions are listed and the action to be taken when a specific condition arises is predetermined so that simulation or production can be automatically executed.
Furthermore, all the aforesaid methods are characterized in that it is necessary not only to make the initial plan but also to feedback actual results for replanning at any time or periodically.
The above methods, however, have the following disadvantages.
The first explosion of orders into component requirements does not have a sequence explosion function, so it is not useful for checking the resource load.
The second explosion of orders into operation/resource requirements does not have a component explosion function, so it is not useful for checking the material requirements or grasping their interrelationship.
The third PERT technique does not have component explosion function and lacks the concept of a process chart, so standardization and automated processing are difficult to be executed. As a result, it is not easy to incorporate changes into a new plan. Also, because this method is composed of a network, expediting is practically difficult.
The fourth Gantt chart lacks the concept of the bill of materials and process chart, so standardization and automated processing are difficult to be attained, and as a result it is not easy to incorporate changes into a new plan, and furthermore, it is difficult to grasp the relations among the items listed on the chart.
The fifth sequence control lacks the concept of component explosion, so the relations among components is difficult to be grasped, and further more, any change in sequence control is difficult because it is preprogrammed, and flexible measures are difficult to be preprogrammed.
Therefore, with these conventional methods, methods which are not related to each other are employed when the respective hierarchies from the overall enterprise level down to the controller level are intended to be entirely or partially integrated as represented by computer integrated manufacturing (CIM). Thus, not only the existing systems but even systems being planned are difficult to be interfaced with each other and the accomplishment of integration will be difficult.